Resistance welding or spot welding is commonly applied to the assembly of automotive bodies and other products. The guns are often large to accommodate large sheets of steel requiring welds far from a convenient access location. These guns are generally held and manipulated by robots or held by hoists and manually manipulated. Traditionally the guns are made of strong metal structural elements to withstand the welding forces that must be applied to the weld electrodes. Consequently the guns may have very large mass which is difficult for a robot or other machine to manage with consistent positioning accuracy over an extended period of time due to wear in the robot wrist, for example. The heavy guns tend to have lifetimes limited by fatigue.
There have been some attempts to make light weight weld guns from composite materials which are strong but not as heavy as the traditional metal structures. Generally such structures have been formed by packing resin impregnated fibers or fabrics into a mold with random fiber orientation and curing the resin to obtain an isotropic product, i.e., a product which has no preferential load direction to withstand stress. Such devices have achieved light weight and dimensional stability but have exhibited short lives. Further, in order to fabricate such a device an expensive mold must be made.